Don't forget that children breathe in 50% more air per pound of body weight than adults
|   Feb 01, 2017
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Don't forget that children breathe in 50% more air per pound of body weight than adults

Children’s exposure to air pollution is a special concern because their immune system and lungs are not fully developed when exposure begins, raising the possibility of different responses than seen in adults. In addition, children spend more time outside, where the concentrations of pollution from traffic, power plants, and other combustion sources are generally higher. Although air pollution has long been thought to exacerbate minor acute illnesses, recent studies have suggested that air pollution, particularly traffic-related pollution, is associated with infant mortality and the development of asthma and atopy.             

Why are children more susceptible to the harmful effects of air pollution? 
Children breathe more air per pound of body weight, so their exposure to air pollution is much greater than adults.  Children’s organs, including their lungs, develop until they reach their late teens, usually around the age of 18.  Studies show that developing organs are sensitive to the toxic effects of air pollutants and environmental toxins and that children absorb pollutants more readily than adults and retain them in the body for longer periods of time. According to the World Resources Institute, “Because they breathe at a higher rate than adults, children are exposed to greater levels of pollution relative to their smaller body weight and are generally more sensitive to their effects on a pound-for-pound basis.”

What are the effects of air pollution on children’s health and development?
 In 2005, the World Health Organization published a review of studies conducted around the world in recent decades, to better understand the effects of air pollution on the health of children. The following are some of the important findings of this review:

  • The intrauterine, perinatal and early childhood periods are vulnerable times when the lungs are especially susceptible to injury by air pollutants. Exposure during these periods reduces the maximal functional capacity achieved in adult life and can lead to enhanced susceptibility during adulthood to infection due to the effects of pollutants such as tobacco.
  • Children with underlying chronic lung diseases, particularly asthma and cystic fibrosis, are especially vulnerable and are at greater risk of adverse effects from pollution than healthy children.
  • There is now substantial evidence on the adverse effects of air pollution on different pregnancy outcomes and infant health. The evidence shows that air pollution, (with concentrations typical of many European cities), increases the risk of death from respiratory causes in the postneonatal period.
  • The evidence also shows a relationship between exposure to ambient air pollutants and adverse effects on the development of lung function. Reversible lung function deficits chronically reduced lung growth rates and lower lung function levels are associated with exposure to air pollution. This evidence shows clearer relationships for particulate matter and traffic-related air pollution (indicated by nitrogen dioxide) than for other pollutants.
  • Based on current knowledge, air pollutants seem to interact with other environmental factors, such as allergens, viruses, and diet, that influence the overall impact of air pollutants on children’s health.
  • The report concludes that there is a causal relationship between exposure to air pollutants and aggravation of asthma. The evidence is also sufficient to assume a causal link between exposure to particulate matter and increased prevalence and incidence of a cough and bronchitis.
  • Environmental contaminants such as certain heavy metals and persistent organic pollutants show significant adverse effects on the development of the nervous system and behavior in children. Also, there is sufficient evidence of a causal relationship between exposure to lead and neurobehavioral deficits in children, in terms of cognitive impairment.

Local evidence: Children in Delhi
A massive 2010 study by the Chittaranjan National Cancer Research Institute, Kolkata, looked at the health effects of air pollution on over 11,000 school children in Delhi. Some important findings:

  • Compared to the control group, Delhi’s kids had 1.8 x more respiratory illnesses (sinusitis, running or stuffy nose, sneezing, sore throat and common cold with fever) and 2 x lower respiratory illnesses. frequent dry cough, sputum-producing cough, wheezing breath, breathlessness on exertion, chest pain or tightness and disturbed sleep due to breathing problems).
  • Respiratory symptoms were more prevalent in children from lower socio-economic status and least in children from families with higher economic status.
  • The symptoms were more prevalent in winter when levels of particulate matter are highest, and least prevalent during monsoon season when particular matter is lowest
  • The results showed a reduction in lung function of 43.5% of the Delhi school kids, compared to 25.7% in the control group.

Lung function reduction was more prevalent in the girls in both settings than in the boys.  Air pollution is linked to disease and infections that kill around 600,000 children under 5 years of age per year. Pneumonia accounts for up to 16% of all under 5 deaths more than half of childhood deaths are associated with air pollution.

Globally, according to the World Health Organization, indoor air pollution killed about 4.3 million people and outdoor air pollution killed about 3.7 million in 2012.Focussing on under-5 mortality, the World Health Organization found that approximately 531,000 children under the age of 5 died from household air pollution in 2012, and around 127,000 children under the age of 5 died from outdoor air pollution in 2012.

A 2016 comparative risk assessment of the Global Burden of Disease 2015 study found similar estimates. It found that air pollution exposure was linked with almost 6.5 million deaths worldwide (ranging from 5.7–7.3 million), with 4.2 million due to outdoor air pollution (ranging from 3.7–4.8 million), and just under 2.9 million due to indoor air pollution (ranging from 2.2–3.6 million). For outdoor air pollution, this represents a considerable increase compared to 2013 estimates, when it was linked to 2.9 million deaths. The number of indoor air pollution deaths remained largely the same between both 2013 and 2015 studies.

As air pollution continues to grow, so too will mortality. One meta-analysis of 108 studies found that with every 10 μg/m increase in short-term particulate matter exposure, there is approximately a 0.34 percent increase in the risk of death among younger populations in particular. Other research shows even more severe effects among adults: 10μg/m increase in exposure to particulate matter increased the risk of premature death by 3 percent. World Health Organization guidelines indicate that premature mortality could be reduced by up to 15 percent where PM10 is reduced from 70 to 20 μg/m. Air pollution is linked not only with diseases that kill but also with poor health and morbidity among millions of more children. It causes difficulty breathing. Studies show it is linked with asthma, bronchitis, airways inflammation and even eye irritation. It can cause wheezing, coughing and phlegm production.

Children who breathe polluted air are at higher risk of potentially severe health problems, in particular, acute respiratory infections such as pneumonia. When these diseases do not kill them, they still severely affect their overall health and development. Exposure can also affect lung growth among children, as the cell layer on the inside of the respiratory tract is more permeable among young children. A mother’s chronic exposure to severe air pollution during pregnancy is linked with low birth weight at term, intrauterine growth retardation and small for gestational age embryos. Air pollution also contributes to at least half of all pneumonia cases. Evidence suggests that air pollution can cause oxidative stress and inflammation in the smaller airways, leading to the exacerbation of asthma and chronic bronchitis, airway obstruction and decreased gas exchange. It can also undermine normal lung antimicrobial defense functions by interfering with the clearance and inactivation of bacteria in the lung tissue. Health complications can then last throughout the rest of their lives. Studies show that halving of indoor air pollution exposure with a chimney stove rather than open fires reduced severe pneumonia by 33 per cent.

Evidence of the impact of air pollution on cognitive development is also found through its impact on the fetus. Studies have shown that because these particles enter the bloodstream, they can also cross the placental barrier and affect the development of the fetus, including both physical and cognitive development. Several studies have shown that pregnant women’s exposure to polycyclic aromatic hydrocarbons (PAHs) (a pollutant associated with fossil fuel combustion) affects the white matter of the unborn child’s brain significantly – which is responsible for the communication between different parts of the brain. In consequence, studies have shown that PAHs can cause future developmental delays, lower verbal IQ, and increased signs of anxiety, depression, and problems with attention. Even very low levels of PAHs and lead in a child’s blood have been found to result in cognitive delays.

The links between cigarette smoking and cognitive development have also been firmly established, including where pregnant mothers are exposed to either primary or secondary cigarette smoke. Recycling of valuable elements has become a source of income mostly in the informal sector, often by burning other elements to retrieve valuable materials. For example, burning of e-waste, such as televisions, computers and mobile phones, is done to extract metals like copper or gold. This process also often produces toxic fumes. E-waste recycling workers are often women or children. Their continuous exposure to concentrated levels of air pollutants like lead, aluminum and zinc has devastating consequences, including birth defects and infant mortality. Other studies found that children at e-waste recycling sites were reported to suffer from breathing ailments, skin infections and stomach diseases as well as significantly higher levels of leukaemia.

We can easily conclude that the effect of pollution on children are increasingly better known, even though for now this knowledge has not brought about significant changes in the behavior of the general population. A great many chemical substances are suspended in polluted air and are breathed in daily, constituting a particular risk for children. This is due in part to the immaturity of children’s immune and respiratory systems, but also to the fact that they tend to spend more time outdoors in the afternoon and in the summer when contamination is higher. On the other hand, we should not forget that children breathe in 50% more air per pound of body weight than adults, and thus a correspondingly higher amount of pollutants. Besides this, children are not able to perceive the initial symptoms that should act as the warning signs for late onset problems, rendering them unable to take necessary measures to reduce exposure to contaminated air.

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